The present invention relates to the field of perfumery. It concerns, more particularly, the compounds of formula 
wherein X represents a Cxe2x89xa1N group or a C(H)xe2x95x90O group and the C5-ring is either saturated or carries a double bond in one of the positions indicated by the dotted lines, or any mixture of two or more compounds of formula (I), and their use in perfumery.
The compounds as defined by the above formula (I) are novel compounds, and their use in perfumery has never been described or suggested. They carry an aldehyde function or a nitrile function and all have a characteristic, green-lemon type odor which is of considerable value in perfumery.
One embodiment of the invention is drawn to the compounds of the above formula (I) in which X is a Cxe2x89xa1N group, i.e. belonging to the nitrile chemical family, which are particularly appropriate for use in aggressive media. A further embodiment are the corresponding aldehydes of similar chemical structure which show the same odor type as the said nitriles.
It should be mentioned that a large number of compounds belonging to the nitrile chemical family are known in the perfume industry. In the context of the present invention, one can cite the nitrites specified hereinafter, which are currently used in perfumery, in particular in functional perfumery.
Geranyl nitrile (3,7-dimethyl-2,6-octadienenitrile) possesses a strong green, chemical odor resembling that of citral (Z-3,7-dimethyl-2,6-octadienal), the latter being itself a compound of widespread use in perfumery applications and of natural occurrence.
Citronellyl nitrile (3,7-dimethyl-6-octenenitrile) shows an olfactive note reminiscent of the odor of lemon, with an undernote characteristic of the nitrites. The citrus note is likewise quite pronounced in Ozonil(copyright) (mixture of 2-tridecenenitrile and 3-tridecenenitrile; origin: Haarmann and Reimer, Germany), but there are also present notes of the mandarine-fruity, peach type, which are associated with a floral undernote.
Finally, citronitrile (3-methyl-5-phenyl-2-pentenenitrile) shows an odor of the same type as the compounds mentioned beforehand, namely of the fruity-citrus type.
Detergents, deodorants or antiperspirants and soaps are examples of products which are aggressive media, in which citral, for example, which can be considered as the typical compound representing the citrus-type odor, with its powerful citrus-green note, is unstable, preventing it from being used in functional perfumery, and this in spite of its odor which is very prized by perfumers.
Now, in spite of showing olfactive similarities with citral, the known nitrites described above do not possess its olfactive quality. Their odor notes are less characteristic of lemon, less fresh-citrus, and a fatty-metallic connotation is found in all these nitrites. For these reasons, the search for nitrites stable in aggressive media and possessing an odor close to the citrus-green note of the odor of citral continues to be a task of actuality.
The present invention provides novel compounds having this desired odor and brings an original solution to exactly this problem.
We have in fact found that, in particular, the compounds of formula 
having a double bond in one of the positions indicated by the dotted lines, or any mixture of two or more of these compounds, not only possess an excellent stability in aggressive media, but also an odor which is very similar to that of citral.
Thus, the odor of the compounds of formula (Ixe2x80x2), or of the mixtures of these, possess the same fresh-citrus connotation as citral, quite unexpected for a nitrile. There is also found a green connotation reminiscent of lime, and the compounds of the invention do not have the fatty-metallic connotation generally found in nitrites of current use in perfumery (see above for current examples). Generally speaking, the odor of the compounds of the invention is very fresh and clean.
According to the invention, it is preferred to use as perfuming ingredient, a mixture of the compounds of formula (Ixe2x80x2) containing at least about 30% by weight of the compound of formula 
Even more preferred are the above-mentioned mixtures containing, besides the compound (Ixe2x80x2a) in the specified amount, about 60% by weight of the compound of formula 
having an endocyclic double bond in position 3xe2x80x2 of the ring.
According to an even more preferred embodiment of the invention, there will be used a compound of formula (Ixe2x80x2a) in its pure state, representing at its best the fresh-citrus, green-lime note of citral.
It has however been found that the above-mentioned olfactive characteristics are also present in the mixtures as specified above, satisfactory for the perfumers"" criteria and thus the said mixtures are also useful as perfuming ingredients. The advantage of the use of these mixtures, compared to that of the compounds contained therein in their pure state is an economical one, given the fact that these mixtures can be directly obtained from the synthesis described below, without requiring the use of particular separation techniques.
The nitrites of the present invention are accessible by a multi-stage synthesis which makes use of 3-isopropenyl-1,2-dimethyl-1-cyclopentanol, or one of its optically active isomers, as starting product. This cyclic alcohol is a commercially available compound, formed in the pyrolysis reaction of (xe2x88x92)-R-linalool and leading to a mixture of four diastereomers (see H. Strickler, G. Ohioff and E.sz.Kovàts, HelV. Chim. Acta 1967 50, 759).
The synthesis we have developed for the nitrites of formula (I) is outlined in the scheme below: 
The first step of this synthesis comprises the hydroformylation of the cyclic starting alcohol, to form the corresponding aldehyde. The hydroformylation reaction being known to a person skilled in the art, the latter can choose the appropriate reaction conditions, for example the catalyst, solvent or pressure giving good results, without a more detailed description being necessary here.
The thus-obtained aldehyde is then transformed into the corresponding nitrile, for example by using hydroxylamine or a salt thereof, in the presence of a base. In the following step, the compound obtained is esterified with a current esterifying agent, for example acetic anhydride. It was found to be advantageous not to isolate the above-mentioned intermediate nitrile from the reaction mixture, but to directly esterify said nitrile in the same medium in which it had been prepared.
The last step of the process is the elimination reaction of the thus-obtained ester (II), preferably of 3-(2xe2x80x2-cyano-1-methylethyl)-1,2-dimethyl-1-cyclopentyl acetate, leading to the desired final product, namely the unsaturated nitrites of formulae (Ixe2x80x2a) and (Ixe2x80x2b). The elimination reaction can be carried out under various conditions which are known to a person skilled in the art. In this context, one should mention the use of an acid, for example p-toluenesulfonic acid, to carry out the elimination reaction.
The best results were however obtained by a thermal treatment, i.e. a pyrolysis of the nitrile ester, resulting in a crude product containing an olfactively satisfactory amount of the most desired nitrile (Ixe2x80x2a), whereas the elimination reaction with an acid often results in the preferential formation of nitrites having double bonds in endocyclic position, i.e. those of above formula (Ixe2x80x2b) and of formula (Ixe2x80x2c) below: 
which are less appreciated from an olfactive point of view.
We have found that products containing about 30% by weight of the nitrile of formula (Ixe2x80x2a) could be obtained when the pyrolysis reaction was carried out at a temperature range from about 400 to 550xc2x0 C., preferably from about 430 to 500xc2x0 C., and under a pressure from about 10 to 50xc3x97102 Pa. These mixtures contain, besides the compound (Ixe2x80x2a), the nitrites of formulae (Ixe2x80x2b) and (Ixe2x80x2c), with their respective amounts varying according to the conditions employed.
These mixtures can be used as such as perfuming ingredients, since they have all the olfactive characteristics of the nitrile (Ixe2x80x2a), i.e. the typical fresh-citrus, green-lemon note, the overall impression being practically as good as that of this nitrile in its pure form.
It is of course possible to use mixtures of the above-described type containing amounts of the nitrile (Ixe2x80x2a) different from the quantity mentioned above (30% by weight), as long as said nitrile is present in an effective amount, i.e. in an amount sufficient to bring out the olfactive character of the mentioned nitrile. We have however found that mixtures containing 30% or more of this nitrile were preferred according to the invention.
Of course, since the pyrolysis reaction of (xe2x88x92)-(R)-linalol results in a mixture of four diastereomers which each can be isolated by current techniques, each of these diastereomers can then be used separately to prepare the desired nitrites, the stereochemistry of the latter being thus determined by that of the starting diastereomer employed, which remains unchanged throughout the synthesis outlined above. This will become more obvious from the study of the examples further on. According to their stereochemistry, the odor of the compounds of formula (Ixe2x80x2a) having a defined stereochemistry can be different from that of a mixture of diastereomers.
It was found that the best olfactive quality is obtained when the cyclopentanol used as starting product has the configuration (1R,2S,3S), resulting in a mixture which is composed of the nitriles of formula (Ixe2x80x2a) having the configuration (1xe2x80x2R,2xe2x80x2S,3S) and (1xe2x80x2R,2xe2x80x2S,3R) and the nitrites of formula (Ixe2x80x2b) having the configuration (1xe2x80x2R,2xe2x80x2S,3R) and (1xe2x80x2R,2xe2x80x2S,3S). These mixtures, and in particular the stereoisomers of formula (Ixe2x80x2a) as described above, are preferred according to the invention.
A nitrile mixture of almost similar quality was obtained with the cyclopentanol of configuration (1R,2R,3R), resulting in a final mixture of the nitrites of formula (Ixe2x80x2a) of configuration (1xe2x80x2S,2xe2x80x2R) and of formula (Ixe2x80x2b) of configuration (1xe2x80x2S,2xe2x80x2R).
The olfactive quality of the mixture obtained from the cyclopentanol of configuration (1R,2S,3R), i.e. of the mixture of nitrites of formula (Ixe2x80x2a) having the configuration (1xe2x80x2S,2xe2x80x2S) and the nitrites of formula (Ixe2x80x2b) having the configuration (1xe2x80x2S,2xe2x80x2S), is inferior to the quality of the nitrites obtained above. Here, the lemon note is weaker, and fatty and powdery connotations are perceived, the floral-citrus note being still clearly present, however.
The compound 3-(2,3-dimethyl-1-cyclopentyl)butanenitrile of formula (Ixe2x80x2d) (see Scheme II below), having a saturated C5-ring, has also been found to possess the typical green-lemon note in its odor, with a slight nitrile connotation.
A further embodiment of the invention are the aldehydes of the formula (Ixe2x80x3) represented below having a double bond in one of the positions indicated by the dotted lines or any mixture of two or more of these compounds. The following Scheme (II) outlines the synthesis for these aldehydes, as well as the synthesis for the corresponding ring-saturated aldehydes of formula (Ixe2x80x3a). 
The ring unsaturated aldehydes of formula (Ixe2x80x3) are useful in perfumery due to their fresh-citrus and green-lemon type note with a typical aldehyde connotation. The odor type is close to that of 3,5,5-trimethylhexanal (isononylaldehyde), which is a compound of widespread use in perfumery, capable of imparting notes of the green type to a composition.
The corresponding ring saturated aldehyde (Ixe2x80x3a) has a green-citrus type odor, with an earthy and slightly metallic connotation and a lemongrass type undernote.
The nitriles of the present invention were found to be completely stable in a lot of typically aggressive media for perfumes. In this context, there can be cited detergents containing bleaching agents and activators such as, for example, tetraacetylethylenediamine (TAED), hypohalites, in particular hypochlorite, peroxygenated bleaching agents such as, for example, perborates, etc. One can also cite body deodorants and antiperspirants containing for example aluminum salts.
Generally speaking, the nitrites of the present invention are preferably employed in applications like soaps, shampoos, body deodorants and antiperspirants, solid or liquid detergents for the treatment of textiles, fabric softeners, or yet detergent compositions or all-purpose cleaners for the cleaning of dishes or various surfaces, whether they are intended for household or industrial use.
Of course, the use of the nitrites of the invention is not limited to the above-mentioned products, they lend themselves to all other current uses in perfumery, namely the perfuming of soaps and shower gels, hygiene or hair-care products, as well as of body deodorants, air fresheners or yet cosmetic preparations, and even for the use in fine perfumery, namely in perfumes and colognes.
The aldehydes of the present invention can also be used in all the applications cited above.
In all cited applications, the compounds of the invention can be used alone or in admixture with other perfuming ingredients, solvents or adjuvants of current use in the art. The nature and the variety of these coingredients do not require a more detailed description here, which, moreover, would not be exhaustive, and the person skilled in the art will be able to choose the latter through its general knowledge and as a function of the nature of the product to be perfumed and of the desired olfactive effect.
These perfuming ingredients belong to chemical classes as varied as alcohols, aldehydes, ketones, esters, ethers, acetates, nitrites, terpene hydrocarbons, sulfur- and nitrogen-containing heterocyclic compounds, as well as essential oils of natural or synthetic origin. A large number of these ingredients is moreover listed in reference textbooks such as the book of S. Arctander, Perfume and Flavor Chemicals, 1969, Montclair, N.J., USA, or its more recent versions, or in other works of similar nature.
The proportions in which the compounds according to the invention can be incorporated in the various products mentioned beforehand vary within a large range of values. These values depend on the nature of the article or product that one desires to perfume and the odor effect searched for, as well as on the nature of the coingredients in a given composition when the compounds of the invention are used in admixture with perfuming coingredients, solvents or adjuvants of current use in the art.
As an example, there can be cited typical concentrations of the order of 0.1 to 10%, or even more, by weight of these compounds relative to the weight of the perfuming composition in which they are incorporated. Far lower concentrations than those mentioned above can be used when the compounds are directly applied for perfuming the various consumer products cited beforehand.